My vote goes for CaptureNX. But you need a capable hardware, otherwise it will only creep. It's all nondestructive editing and very good when you shoot RAW, as you can do all the in-camera-adjustments later on (e.g. WB). But even with jpgs: you can convert them into RAW and have all the non-destructive editing with roll-back etc. for your pics. Only the in-camera adjustments are disabled, when you have converted the RAW from an original jpg.
And it's easy enough even for a lazy guy like me -----------
P.S.: ou can have a free 30 day trial and read more about it here.

How about Adobe Lightroom? I use that and I think it's quite easy to use and with most of the editing controls that I need, anything more and I would probably need Photoshop anyway. The noise reduction and sharpening tools are pretty basic though and it doesn't have any tools to correct distortion, if you need that kind of thing. It keeps a history of all changes made and allows you to make virtual copies so you can do a before and after kinda thing. It runs fine if on my PC even though I only have 1gb of ram unless I view RAW files.